JobRunr: InstantiationException in ReflectionUtils.newInstance

I'm using JobRunr 6.3.0 for scheduling recurring background jobs in Java, and I encounter a problem with reflective access.

I'm trying to have an abstract class that implements the job scheduling logic, creating one job that calls an abstract method which is implemented in each child class. Like this:

public abstract class Blubb {

    public Blubb() {
        this(...defaultArgs);
    }

    protected Blubb(defaultArgs) {
        // set up
    }

    protected abstract String name();

    protected abstract Iterator<Object> getObjectsFromExternalSource();

    public void load() {
        JobScheduler scheduler = JobRunr
            .configure()
            .useStorageProvider(new InMemoryStorageProvider())
            .useBackgroundJobServer()
            .initialize()
            .getJobScheduler();

        scheduler.createRecurrently(
            RecurringJobBuilder
                .aRecurringJob()
                .withId(name())
                .withDuration(Duration.ofSeconds(10))
                .withDetails(this::run)
                .withAmountOfRetries(2)
        );
    }

    public void run() {
        Iterator<Object> objects = getObjectsFromExternalSource();

        while (objects.hasNext()) {
            // do stuff
        }
    }
}

Job creation works, and the job in the database looks fine:

{
  "_id": "name",
  "version": 0,
  "jobAsJson": "{\"version\":0,\"jobSignature\":\"org.example.blah.Blubb.run()\",\"jobName\":\"org.example.blah.Blubb.run()\",\"amountOfRetries\":2,\"labels\":[],\"jobDetails\":{\"className\":\"org.example.blah.Blubb\",\"staticFieldName\":null,\"methodName\":\"run\",\"jobParameters\":[],\"cacheable\":true},\"id\":\"name\",\"scheduleExpression\":\"PT10M\",\"zoneId\":\"Etc/UTC\",\"createdAt\":\"2023-08-25T06:39:29.844981739Z\"}",
  "createdAt": {
    "$numberLong": "1692945569844"
  }
}

But everytime it tries to run the job, I get the following exception:

WARN  o.j.server.BackgroundJobPerformer - Job(id=a444fd50-843a-4464-88a1-e51530056b3f, jobName='org.example.blah.Blubb.run()') processing failed: An exception occurred during the performance of the job
org.jobrunr.JobRunrException: JobRunr encountered a problematic exception. Please create a bug report (if possible, provide the code to reproduce this and the stacktrace)
    at org.jobrunr.JobRunrException.shouldNotHappenException(JobRunrException.java:43)
    at org.jobrunr.utils.reflection.ReflectionUtils.newInstance(ReflectionUtils.java:156)
    at org.jobrunr.server.runner.AbstractBackgroundJobRunner$BackgroundJobWorker.getJobToPerform(AbstractBackgroundJobRunner.java:46)
    at org.jobrunr.server.runner.AbstractBackgroundJobRunner$BackgroundJobWorker.run(AbstractBackgroundJobRunner.java:36)
    at org.jobrunr.server.runner.AbstractBackgroundJobRunner.run(AbstractBackgroundJobRunner.java:20)
    at org.jobrunr.server.BackgroundJobPerformer.runActualJob(BackgroundJobPerformer.java:89)
    at org.jobrunr.server.BackgroundJobPerformer.performJob(BackgroundJobPerformer.java:64)
    at org.jobrunr.server.BackgroundJobPerformer.run(BackgroundJobPerformer.java:42)
    at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:539)
    at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
    at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:304)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
    at java.base/java.lang.Thread.run(Thread.java:833)
Caused by: java.lang.InstantiationException: null
    at java.base/jdk.internal.reflect.InstantiationExceptionConstructorAccessorImpl.newInstance(InstantiationExceptionConstructorAccessorImpl.java:48)
    at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:499)
    at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:480)
    at org.jobrunr.utils.reflection.ReflectionUtils.newInstance(ReflectionUtils.java:154)

Any idea what I'm doing wrong? Is this a problem with the class constructors? I have a public no-args constructor and an additional protected constructor in both the abstract class above and in the child classes. And I think it used to work before, when I only had one public default constructor.